Miniature circular DIN connectors are employed with computers, audio equipment, video equipment and other electrical components to enable the connection of one such component to another. Miniature circular DIN connectors comprise a plurality of pin or socket terminals which are mounted in a nonconductive housing and which are electrically connected to conductive leads. One such DIN connector may be mounted to a panel or circuit board of an electrical component, with the terminals of the DIN connector being electrically connected to conductive areas on the panel or circuit board. A mating DIN connector may then be mounted to a cable, with the terminals thereof being electrically connected to conductive wire leads within the cable. Typically, the board mounted miniature circular DIN connectors will define receptacles with pin-receiving terminals therein, while the cable mounted DIN connectors define plugs with pin terminals therein. The cable may include a second DIN connector plug on its opposed end for electrical mating to a miniature circular DIN connector in a related electrical component. In this manner, for example, the keyboard or mouse of a personal computer may be joined to the central processing unit thereof. The number and arrangement of pins or sockets in the miniature circular DIN connector can vary, with most DIN connectors having between three and nine terminals therein. The particular arrangement of terminals in the DIN connector and the construction of the housings are intended to ensure polarized mating of the respective terminals.
The board mounted miniature circular DIN receptacles will include terminals having solder tails, surface mountable contacts or other such contact means for making electrical connection to appropriate conductive portions of the circuit board. The very high circuit density on the board requires extremely accurate positioning of the board contact means of each terminal to ensure that the circuits are properly completed by the DIN connector. This accuracy becomes both more difficult and more important as the circuit density increases and as the DIN connector size decreases.
Government agencies maintain strict EMI standards to ensure that electromagnetic energy generated by cables and electrical equipment does not interfere with other electrical equipment or telecommunications equipment. The United States Federal Communications Commission maintains rigid standards to control the levels of EMI.
DIN connectors generally are considered to be a potential location on an electrical apparatus from which EMI may be emitted. As a result, most DIN connectors are provided with a shield to control EMI. The shield typically will comprise an annular metallic member that surrounds the terminals and is grounded to the board. The grounded shielding is intended to prevent or control the dissipation of electromagnetic energy.
The circuit density in virtually all electrical components has dramatically increased in recent years due to a general reduction in the size of the components and/or an increase in the complexity of the circuitry. The greater circuit density has required correspondingly smaller electrical connectors of all sorts, including the miniature circular DIN connectors. Furthermore, the increased circuit density in the vicinity of electrical connectors has substantially reduced the options available for achieving certain functions, such as controlling EMI. Additionally, the smaller electrical connectors required by the increased circuit densities have made it extremely difficult to provide socket terminals that can exert acceptable contact pressure while simultaneously exhibiting adequate resiliency after several connections and reconnections. In this regard, it should be realized that miniature circular DIN connectors used in currently marketed computers may define a cube of only approximately 0.50 inch square (e.g., about 1.25 cm) within which 3-9 terminals and the necessary EMI shields are disposed. The 3-9 terminals within this 0.50 inch (1.25 cm) square DIN connector may be required to exert normal mating contact forces of between 50-100 grams per contact, and may be required to perform satisfactorily after repeated mating and unmating operations.
An extremely effective miniature terminal that can be incorporated into a miniature circular DIN connector is disclosed in co-pending patent application Ser. No. 255,001 which was filed on Oct. 6, 1988, by Dominique Bertho et al and which is entitled "ELASTICALLY SUPPORTED DUAL CANTILEVER BEAM PIN-RECEIVING ELECTRICAL CONTACT". Co-pending application Ser. No. 255,001 is assigned to the assignee of the subject invention, and the disclosure thereof is incorporated herein by reference. Co-pending patent application Ser. No. 255,001 does not specifically address structures for dealing with EMI in miniature DIN connectors. Similarly, co-pending application Ser. No. 255,001 does not address the difficulties associated with the secure and accurate disposition of terminals in a DIN connector.
The prior art does include attempts to provide EMI shielding for DIN connectors. For example, U.S. Pat. No. 4,493,525 which issued to Hall et al on Jan. 15, 1985 shows a DIN receptacle having an annular groove with a communicating recess which is adapted to receive a grounding spring for contacting the mating shield on a plug. No outer shield for the connector housing is provided in U.S. Pat. No. 4,493,525. However, in certain embodiments, a front shield extends entirely across the front face of the connector. Structures very similar to those shown in certain embodiments of U.S. Pat. No. 4,493,525 are also shown in German Patent Publication No. 1,515,850 which was published on Jan. 2, 1970 and in German Patent Publication No. 2,733,634 which was published on Feb. 8, 1979.
Another DIN connector which employs an EMI shield is shown in U.S. Pat. No. 4,637,669 which issued to Tajima on Jan. 20, 1987. The connector of U.S. Pat. No. 4,637,669 includes a base which is mountable to a circuit board, panel or the like and a housing which is mountable to the base. The housing is constructed to loosely receive a plurality of conductive terminals at central locations therein, and is further provided with means for receiving an annular shield around portions of the housing in which the terminals are mounted. The DIN connector shown in U.S. Pat. No. 4,637,669 further includes an external shield which is electrically and mechanically connected to the annular internal shield of the connector. The external shield is constructed to extend across the top of the DIN connector housing, down two opposed side walls of the housing and into proximity to the circuit board. The three-sided external shield of U.S. Pat. No. 4,637,669 and the annular internal shield connected thereto are intended to function as a single effective EMI shield.
Many DIN connectors with EMI shielding are constructed to provide the shield for EMI generated at the cable/DIN interface. It has now been found, however, that in many applications a greater amount of EMI is generated from the computer or other such electrical component to which the DIN connector is mounted. In many such situations, the EMI shield intended to shield the cable/DIN connector interface will actually function as an antenna that will generate rather than suppress the greater levels of EMI generated from the electrical component to which the DIN connector is mounted. In some situations, for example, the interconnection of internal and external EMI shields will create a loop that may function as an antenna.
In view of the above, it is an object of the subject invention to provide a miniature circular DIN connector having enhanced EMI shielding.
It is another object of the subject invention to provide a miniature circular DIN connector that is effective in shielding EMI generated by both the cable/ connector interface and by the electrical component to which the DIN connector is mounted.
It is an additional object of the subject invention to provide a miniature circular DIN connector where the EMI shield does not function as an antenna that would radiate certain types of EMI.
A further object of the subject invention is to provide a miniature circular DIN connector that can be manufactured in a very small size while still providing acceptable contact forces and an ability to repeatedly connect and disconnect.
Still another object of the subject invention is to provide a miniature circular DIN connector which accurately positions the board contact means of the terminals therein.
Yet another object of the subject invention is to provide an external shield for a miniature circular DIN connector that provides a substantially maximum external surface area.
Another object of the subject invention is to provide direct electrical connection between the external shield of the miniature circular DIN connector and the shield of a mateable DIN connector plug.